1. Field of the Invention
This invention relates generally to computer systems and more particularly to a generic bus interface capable of communicating with a variety of microprocessors.
2. Description of the Related Art
Portable consumer electronic devices are pervasive in all aspects of society today. Examples of such devices include personal digital assistants (PDA), mobile phones, pagers, web tablets, etc. These portable devices contain embedded systems that include central processing units (CPU). Due to the narrow range of functions provided by these handheld devices, the CPUs associated with these embedded systems are not required to have as powerful computing power as desktop or laptop CPUs. A number of vendors provide CPUs designed specifically for a type of handheld device. As is well known, the CPUs also include native buses that support the CPUs. Additionally, the devices include a display screen where images are presented under the control of a display controller, such as a liquid crystal display (LCD) controller. The display controller, typically manufactured by a vendor different from the CPU vendor, is customized to include a bus interface that allows the display controller to communicate with specific CPUs through a system bus. Because of the wide variety of the CPUs, the display controllers tend to be customized to interface with a narrow range of CPUs.
FIG. 1 is a schematic diagram of an embedded system including a CPU in communication with a LCD controller. CPU 100 communicates through bus 102 to bus interface 104 of LCD controller 106. The brand of CPU 100 and type of bus 102 dictates the requirements for the bus interface 104 of LCD controller 106. Thus, bus interface 104 of LCD controller 106 is customized for the different types of buses and CPUs on the market. The customization requires LCD controllers with different bus interfaces for each of the different types of buses and CPUs.
Since there are a large variety of CPUs supplied from vendors such as Motorola, Hitachi, Intel, etc. for the portable devices, customization of the display controller's bus interface becomes an expensive proposition to support each of the available microprocessors and their native bus interfaces. That is, different bus interfaces for each CPU must be supported by the supplier of the LCD controller. Since each of the native bus interfaces will have different pins as well as different signals to be accommodated, the management of which interface is associated with which CPU becomes a difficult task. Accordingly, the LCD chip is more complex and less flexible through the customization required by this approach.
The portable consumer electronic devices incorporating the LCD controller are designed to consume low amounts of power since the devices are typically battery powered. In addition, size is constantly being reduced as the devices are designed with portability in mind. Thus, it is not practical to simply combine the different bus interfaces with one LCD controller because of the multitude of interfaces available. That is, if all the bus interfaces were simply added to the LCD controller, the LCD would have a huge pin count for accommodating a large number of signals. As a result, the size of the LCD controller would be prohibitive and the power consumption would increase if each bus interface was simply added to the LCD controller.
As a result, there is a need to solve the problems of the prior art to provide an LCD controller with a generic bus interface having the flexibility of communicating with a variety of microprocessors without complicating the chip architecture or increasing the size of the controller.